SDD学习笔记

Question

一、SDD工作原理
SDD在协议栈中，位于AIX磁盘驱动程序（AIX disk driver）之上，是伪设备驱动程序。
I/O操作经SDD的路径选择后，被送到AIX磁盘驱动程序。工作原理图如下所示：

二、路径选择算法（多路径模式）

主机系统可以配置多条路径，和ESS LUN 通讯。多路径模式下的SDD有一下特征：

1．If an I/O error occurs on a path, SDD does not attempt to use the path

again until 2000 successful I/O operations on an operational path. This

process is known as bypassing a path. SDD bypasses a failing path

twice (until the I/O error count reaches three) and then puts the path in

the Dead state.

2．If I/O errors occur consecutively on a path and the I/O error count

reaches three, SDD immediately puts the failing path into the Dead state.

It uses the same bypass algorithm twice on the failed path while it is in

the Dead state.

3．SDD puts the failed path from the Dead state back into the Open state

after a certain number of successful I/O operations on an operational

path. As listed in Table 1, the required number of successful I/O

operations varies from one host system to another.

If the first I/O operation fails after the path is put back into the Open state,

SDD puts the path into the Dead state immediately and permanently. You

must manually bring the path online by using the datapath command.

Operating System                      Number of I/O operations
AIX                                            50,000
Windows NT                             50,000
Windows 2000                          50,000
HP                                            200,000
Solaris                                       200,000

4．If an I/O error occurs on the last operational path to a device, SDD

attempts to reuse (or fail back to) a previously-failed path. SDD never

puts the last operational path to an ESS LUN into the Dead state even if

I/O errors have occurred on the path.

5．If an I/O error occurs on all the paths to an ESS LUN, SDD returns the

I/O error back to the application.

三、SDD的安装

   操作系统为AIX5.2-ML07

1．  安装FC设备驱动程序（以6239FC卡为例）

需要安装的文件束（可以从AIX安装盘获取）包括：

devices.pci.df1000f9     FC卡驱动程序

devices.fcp.disk         FC磁盘驱动程序

devices.common.IBM.fc  FC和SCSI协议驱动程序

2．  安装ESS磁盘驱动程序

ibm2105.rte

3．  安装SDD驱动程序

devices.sdd.52.rte

SDD驱动程序下载地址：

http://www-1.ibm.com/support/doc ... s=utf-8&lang=en

四、SDD的配置
1．        检查ESS hdisk是否已正确配置
# lsdev -Cc disk |grep 2105
hdisk2 Available 0E-08-02     IBM FC 2105F20
2．        用smitty dev 配置SDD
#smitty dev
  Install/Configure Devices Added After IPL
  Printer/Plotter
  TTY
  Asynchronous Adapters
  PTY
  Console
  MPIO Management
  Fixed Disk
  Data Path Devices
  Disk Array
  CD ROM Drive
  Read/Write Optical Drive
  Diskette Drive
  Tape Drive
  Communication
选择Data Path Devices
                               Data Path Devices

Move cursor to desired item and press Enter.

  Display Data Path Device Configuration
  Display Data Path Device Status
  Display Data Path Device Adapter Status
  Define and Configure all Data Path Devices
  Add Paths to Available Data Path Devices
  Configure a Defined Data Path Device
  Remove a Data Path Device
选择Define and Configure all Data Path Devices
                                 COMMAND STATUS

Command: OK            stdout: yes           stderr: no

Before command completion, additional instructions may appear below.

vpath0 Available  Data Path Optimizer Pseudo Device Driver
SDD vpath0成功配置。执行lspv查看pv信息
# lspv
hdisk0          00cd4e8fdfabe0ef                    rootvg          active
hdisk1          00cd4e8fe348149e                    rootvg          active
hdisk2          00cd4e8fa39cf494                    datavg
vpath0          none                                None

3．用hd2vp，将ESS hdisk的volume group 信息转到SDD vpath 设备
# hd2vp datavg
datavg
datavg contains these hdisks and pvids
   00cd4e8fa39cf4940000000000000000 hdisk2
hdisk2 is part of vpath0.
Deleting pvid of hdisk2 from ODM database
Create vpath0 pvid of 00cd4e8fa39cf494 in ODM database.
lname=vpath0, pvid=00cd4e8fa39cf494
datavg is converted to dpo device vpathes successfully!

# lspv
hdisk0          00cd4e8fdfabe0ef                    rootvg          active
hdisk1          00cd4e8fe348149e                    rootvg          active
hdisk2          none                                None
vpath0          00cd4e8fa39cf494                    datavg

1、SDD常用指令

addpaths

You can use the addpaths command to dynamically add more paths to SDD devices while they are in the Available state. In addition, this command allows you to add paths to vpath devices (which are then opened) belonging to active volume groups.

hd2vp and vp2hd

SDD provides two conversion scripts, hd2vp and vp2hd. The hd2vp script converts a volume group from ESS hdisks into SDD vpaths, and the vp2hd script converts a volume group from SDD vpaths into ESS hdisks. Use the vp2hd program when you want to configure your applications back to original ESS hdisks, or when you want to remove the SDD from your AIXhost system.

Note: You must convert all your applications and volume groups to the original ESS hdisk device special files before removing SDD.

dpovgfix

You can use the dpovgfix script tool to recover mixed volume groups.

lsvpcfg

You can use the lsvpcfg script tool to display the configuration status of SDD devices. This displays the configuration status for all SDD devices.

mkvg4vp

You can use the mkvg4vp command to create a SDD volume group.

extendvg4vp

You can use the extendvg4vp command to extend an existing SDD volume group.

2、启用 SDD trace功能

SDD supports AIX trace functions. The SDD trace ID is 2F8. Trace ID 2F8 traces routine entry, exit, and error paths of the algorithm. To use it, manually turn on the trace function before the program starts to run, then turn off the trace function either after the program stops, or any time you need to read the trace report.

To start the trace function, type:

#trace -a -j 2F8

To stop the trace function, type:

#trcstop

To read the report, type:

#trcrpt | pg

Note: To perform the AIX trace function, you must have the bos.sysmgt.trace fileset installed on your system.

Answer 1

AIX上用mpio+sddpcm多好啊